This invention relates generally to wipes and cloths for use in dusting, and more particularly concerns treatments for non-woven polypropylene webs which increase the webs' ability to attract and hold dust when the webs are used as wipes or dust cloths.
Oils and other additives have long been used in connection with textile woven and non-woven dust cloths and mops to enhance the ability of the cloths or mops to attract and hold dust particles when the cloths or mops are wiped over a surface. Such additives, however, do not always completely adhere to the dust cloths or mops, and tend to smear onto the wiping surface or onto the user's hands. In many applications, such a smeared residue left behind after dusting represents contamination which in certain industrial and commercial contexts cannot be tolerated.
In addition, commercial wipes and dust cloths are increasingly being made from webs of non-woven polyolefinic materials such as polypropylene. Such webs may be made by a melt-blown process which involves heating the polymer resin to form a melt, extruding the melt through a die orifice in a die head, directing a stream of heated fluid, usually air, toward the melt exiting the die orifice to form filaments or fibers that are discontinuous and attenuated, and collecting the fibers on a drum or foraminous belt to form a web. Because the fibers are still tacky when they are collected, they bond together to form an integrated web. Other fibers, such as staple or pulp fibers, may be added to the melt-blown fibers to form a so-called coform web.
The melt-blown process which can be used for making such wipes and dusting cloths is well-known and is described in various patents and publications, including NRL Report 4364, "Manufacture of Super-Fine Organic Fibers" by V. A. Wendt, E. L. Boon, and C. D. Fluharty; NRL Report 5265, "An Improved Device for the Formation of Super-Fine Thermoplastic Fibers" by K. D. Lawrence, R. T. Lukas, and J. A. Young; and U.S. Pat. No. 3,849,241 issued Nov. 19, 1974 to Butin, et al.
Non-woven webs for dusting cloths may also be made by a spun-bond process in which polypropylene is heated and extruded into continuous fine filaments which are randomly cross-laid onto a collecting drum or belt. Because the filaments are still tacky when they are collected, they bond at their points of intersection to form a cohesive web.
In addition, dusting cloths can be made by serially forming layers of spun-bond and melt-blown material one on top of the other to form a web. Because the spun-bond and melt-blown layers are laid down on the same collecting belt within close-timed proximity, the filaments are still tacky so that the layers bond together. Also, laminates of melt-blown and spun-bonded webs may be made for use as dusting cloths.
There is, however, little attraction between dust particles and untreated non-woven polypropylene webs. Dust is collected on such webs primarily due to physical capture of the dust particles by the fibers of the webs, and therefore, it is recognized that additives or treatments are necessary to enhance the dusting capabilities of non-woven polypropylene webs.
While the prior art has not specifically addressed the question of treating non-woven polypropylene webs to enhance their dusting abilities, the prior art does disclose several treatments for polypropylene webs for enhancing other characteristics.
Von Bonin U.S. Pat. No. 4,264,645 discloses treating synthetic polyolefin fleeces with a hydrophilising agent to improve the water vapor absorption capacity of the fleece. The hydrophilising agent is a polymeric organic compound which is a long polymerized chain of polyethylene oxide and polypropylene oxide having molecular weights between about 500 and 8500. While the polymerized hydrophilising agent gives the synthetic fleece material added water absorbing characteristics, the polymerized cross-link chain does not adhere sufficiently to the fleece to assure that if used as a wipe it would not smear.
Takahashi et al. U.S. Pat. No. 4,065,598 discloses a process for imparting anti-static, soil-release, and water-absorbing properties to synthetic polyolefin fibers. In one example (Example 4), polyethylene glycol trimethacrylate is used to treat the polyolefin yarn. The treatment does not appear to enhance the ability of a non-woven polyethylene or polypropylene web to attract dust.